//给定二叉搜索树的根结点 root，返回值位于范围 [low, high] 之间的所有结点的值的和。 
//
// 
//
// 示例 1： 
// 
// 
//输入：root = [10,5,15,3,7,null,18], low = 7, high = 15
//输出：32
// 
//
// 示例 2： 
// 
// 
//输入：root = [10,5,15,3,7,13,18,1,null,6], low = 6, high = 10
//输出：23
// 
//
// 
//
// 提示： 
//
// 
// 树中节点数目在范围 [1, 2 * 10⁴] 内 
// 1 <= Node.val <= 10⁵ 
// 1 <= low <= high <= 10⁵ 
// 所有 Node.val 互不相同 
// 
//
// Related Topics 树 深度优先搜索 二叉搜索树 二叉树 👍 398 👎 0


//leetcode submit region begin(Prohibit modification and deletion)
/**
 * Definition for a binary tree node.
 * public class TreeNode {
 *     int val;
 *     TreeNode left;
 *     TreeNode right;
 *     TreeNode() {}
 *     TreeNode(int val) { this.val = val; }
 *     TreeNode(int val, TreeNode left, TreeNode right) {
 *         this.val = val;
 *         this.left = left;
 *         this.right = right;
 *     }
 * }
 */
class Solution {
    public int rangeSumBST(TreeNode root, int low, int high) {
//        //中序遍历
//        TreeNode p = root;
//        LinkedList<TreeNode> stack = new LinkedList<>();
//        int sum = 0;
//        while (p != null || !stack.isEmpty()) {
//            if (p != null) {
//                stack.push(p);
//                p = p.left;
//            } else {
//                TreeNode pop = stack.pop();
//                // 处理值
//                if (pop.val > high) {
//                    break;
//                }
//                if (pop.val >= low) {
//                    sum += pop.val;
//                }
////                if(pop.val >= low && pop.val <= high)
////                    sum += pop.val;
//                p = pop.right;
//            }
//        }
//        return sum;

        //上下限递归
        if(root == null)
            return 0;
        if(root.val < low){//根节点小于low，递归右子树
            return rangeSumBST(root.right, low, high);
        }
        if(root.val > high){//根节点大于high，递归左子树
            return rangeSumBST(root.left, low, high);
        }
        //在范围内
        return root.val + rangeSumBST(root.left, low, high) + rangeSumBST(root.right, low, high);


    }
}
//leetcode submit region end(Prohibit modification and deletion)
